(i) Electronic configuration:

The general electronic configuration for lanthanoids is [Xe]⁵⁴ 4f^0-14 5d^0-1 6s² and that for actinoids is [Rn]⁸⁶ 5f^1-14 6d^0-1 7s². Unlike the 4f orbitals, the 5f orbitals are not deep sited and participate in bonding with other species to a greater extent.

(ii) Atomic and ionic sizes:

Similar to the lanthanoids, actinoids also exhibit actinoid contraction (overall decrease in atomic and ionic radii). The contraction is more than that of the lanthanoid due to the poor shielding effect of 5f orbitals.